Originally Posted by
DochaDocha
Well, here's the problem with that attitude.
Let's say two first-degree cousins, one male and one female, are the last surviving people on Earth. So, they say to themselves, "We have to procreate, for the survival of our species!" So they have one son and one daughter. Now, the onus on keeping humanity from extinction falls on these two kids, who are both siblings and second cousins, to keep the human race going. That hardly seems fair to demand that a couple of siblings have to procreate for the fate of mankind. And then their kids have to continue the cycle, ad infinitum.
Face it: if humanity ever falls below a certain number, we as a species are toast. Just pack up your things and go home. The same should apply for Kal and Kara.